Immunotherapy of Melanoma With Bortezomib and Interferon-Alpha Resistance to cytotoxic therapy is a hallmark of malignant melanoma. The current standard of care for metastatic disease is single-agent dacarbazine which has an overall response rate of just 15%. Newagents with new mechanisms of action must therefore be explored. Bortezomib (Velcade[unreadable], formerly PS-341) is a novel anti-tumor compound that is a specific and selective inhibitor of the 26S proteasome, a central component of the ubiquitin-proteasome pathway for the degradation of cellular proteins. Treatment of malignant cells with bortezomib leads to growth arrest and apoptotic cell death via multiple mechanisms including altered turnover of cell cycle proteins and blockade of pro-survival signals. We noted that bortezomib-induced apoptosis of melanoma cells was synergistically enhanced in the presence of interferon- alpha (IFN-a), an agent that has unique pro-apoptotic effects of its own. Further analysis revealed that apoptosis was associated with reduced levels of bcl-2 and activation of caspase proteins. Using a murine model of malignant melanoma, we also demonstrated that the survival of tumor-bearing mice was significantly enhanced following treatment with the combination of bortezomib and IFN-a as compared to either agent alone (p = 0.02). We also have preliminary data to suggest that pre-treatment of peripheral blood mononuclear cells with bortezomib leads to prolonged activation of the Jak-STAT signal transduction pathway in response to IFN-a. These are the first experiments to examine the anti-tumor effects of a proteasome inhibitor when combined with a cytokine. We now propose to conduct an investigator-initiated clinical trial of bortezomib and IFN-a2b in patients with metastatic malignant melanoma. We hypothesize that IFN-a will enhance bortezomib-induced tumor cell apoptosis in patients with advanced malignant melanoma. Tumors will be biopsied before and after therapy in order that correlative immunohistochemical stains can be performed. A careful analysis of IFN-a-induced signaling pathways in patient immune cells will also be conducted using a novel flow cytometric assay. These studies will help to define the specific apoptotic and immunostimulatory pathways that are being modulated by the combination of bortezomib and IFN-a2b.